1. Field of the Invention
The present invention relates to a repairing fuse for semiconductor devices. More particularly, the present invention relates to a fuse whose repairing mechanism is conducted in such a way that it is connected with another fuse, instead of being destroyed. Also, the present invention is concerned with a method for fabricating such a repairing fuse.
2. Description of the Prior Art
In semiconductor memory devices, redundancy cells are generally provided by sub-array blocks. For instance, to substitute for defective memory cells by row/column units, redundant rows and columns are prepared in every 256K cell aeries. Typically, after completion of wafer scale integration, testing is conducted to select defective memory cells. If any defective memory cell is detected, programming is executed in the internal circuit to convert its address into that of a corresponding redundancy cell through a repair circuit. Accordingly, if the address corresponding to a defective line is input, the line of the redundancy cells is selected and works in practical use.
Usually, the programming is conducted in an electric fusing technique in which an overcurrent is used to melt a fuse till it disconnects or in a laser beam fusing technique in which a laser beam is used to incapacitate a fuse. Of these techniques, the laser beam fusing technique is preferred by virtue of its simplification and reliability in addition to its ability to be easily laid out. However, this technique suffers from disadvantages in that a control is required to leave an appropriate thickness of a residual oxide on a single layer or multilayer polysilicon structure which is used as a fuse and that the oxide in a small sized fuse box should be etched to a deep extent upon repair (or pad) etching. Another disadvantage of the laser beam fusing technique is that the size of the fuse is inconveniently adjusted to the focal size of the laser beam when shrunk.